The present invention relates generally to infra-red (IR) detectors and particularly concerns a programmable IR detector capable of being used to detect IR signals encoded in numerous different formats.
Many consumer electronics products are operated under the control of IR signals received from a hand-held transmitter. In the transmitter, a control signal is encoded according to a format selected by a particular manufacturer, the encoded control signal being used to modulate a carrier, typically about 40 KH.sub.z, for subsequent transmission as a beam of IR energy. Numerous encoding formats can be employed, such as pulse width modulation in which case a logical "1" bit may be represented by a relatively wide pulse and a logical "0" bit by a relatively narrow pulse. By forming a sequence of data bits in this manner, a control word is formulated representing a selected function of the controlled device. The received signal is initially demodulated to remove the carrier signal, applied to an IR detector and then decoded to activate the selected function.
Due to the fact that the transmitted IR signals are encoded differently by different manufacturers, the IR detection circuits tend also to be unique, being specifically configured according to the encoding format employed. Thus, a given detector circuit is typically suitable for processing only the demodulated IR signals received from the transmitter of a single manufacturer. Such dedicated detection circuits are uneconomical since they are not adaptable for widespread use in receivers from different manufacturers.
It is therefore a basic object of the present invention to provide an economical IR detection circuit capable of use in receivers from diverse manufacturers.
It is a further object of the invention to provide an IR detection circuit which may be programmed for detecting IR signals encoded in different formats.
It is yet another object of the invention to provide an IR detection circuit which may be programmed for precise detection of an encoded IR signal.